The present invention relates to a telephone set having a function of is playing caller data.
In recent years, a visual call waiting service has become popular. The service is that second caller data can be displayed in the call waiting service of a telephone office, i.e. in the service when there is a call from a second caller during talk over the telephone, the line can be switched to the second caller.
FIG. 5 is a block diagram showing a structure of a conventional telephone set, and FIG. 6 is a flow chart for an explanation of the operation of the telephone set.
In FIG. 5, the telephone set comprises an alert-signal detector 2 for detecting an alert signal input through a telephone line 1, an acknowledgment-signal sender 3 for sending an acknowledgment signal when detecting the alert signal through the telephone line 1, a caller-data detector 4 for detecting caller data coming through the telephone line 1, a hook switch 5, storage 6 for storing the caller data obtained by the caller-data detector 4, a controller 7 comprising a microcomputer, and a duplex circuit 8 for sending and receiving the signals of talking and listening through the telephone line 1.
The operation of the telephone set having the above components is described hereinafter.
The telephone set, as shown in the flow chart of FIG. 6, always monitors the input of an alert signal (STEP 1) in its off-hook state and, when an alert signal is input, it sends an acknowledgment signal ACK (STEP 2), then receives caller data which comes after that, then displays and stores the data (STEP 3).
However, in the above structure of the conventional telephone set, there is a problem that the data sounds of the acknowledgment signal and the caller data are heard as noise through the parallel-telephone-set when it is in an off-hook state because the telephone set sends an acknowledgment signal upon receiving the alert signal regardless of the state of the parallel-telephone-set connected to the same telephone line. Also, when there is a public telephone network standard that an acknowledgment signal should not be sent in the state where the parallel-telephone-set connected to the same telephone line is off-hook, the off-hook state of the parallel-telephone-set has to be detected, otherwise the telephone set does not meet the standard.
The telephone set of the present invention comprises an own-telephone-set off-hook detector for detecting the off-hook state of the own-telephone-set, a parallel-telephone-set off-hook detector for detecting an off-hook state of the parallel-telephone-set connected to the same telephone line, a telephone-line-voltage detection circuit for detecting the voltage value of the telephone line, an alert-signal detector for detecting an alert signal input through the telephone line, an acknowledgment-signal sender for sending an acknowledgment signal when the alert-signal detector detects the alert signal, a caller-data detector for detecting a caller-data signals input through the telephone line after the acknowledgment-signal sender has sent the acknowledgment signal, and a controller for controlling the acknowledgment-signal sender not to send an acknowledgment signal when the alert signal is input in a state that the parallel-telephone-set off-hook detector detects the off-hook state of the parallel-telephone-set, and, the telephone set is so composed that the parallel-telephone-set off-hook detector judges the off-hook state of the parallel-telephone-set based on the data detected by the own-telephone-set off-hook detector and the telephone-line voltage value detected by the telephone-line-voltage detection circuit.
The above telephone set of the present invention realizes that the data sounds of an acknowledgment signal and caller data are prevented to be heard as noise through the parallel-telephone-set when it is in an off-hook state, by the method that the acknowledgment-signal sender does not send an acknowledgment signal when the alert signal is input in the state where the parallel-telephone-set off-hook detector detects that the parallel-telephone-set is off-hook.